The vast majority of micro-electronic devices are formed in silicon and, over the last several decades, a substantial effort has been directed to refining the reliability and manufacturability of these devices. As a result, silicon-based microelectronic devices have become dependable and inexpensive commodity items. Particularly, Complementary Metal Oxide Semiconductor (CMOS) technology has become a multi-billion industry providing the basis manufacturing technology for nearly 80° AD of all electronic commodities to society. Furthermore Silicon-on-Insulator (SOI) technology is regarded as a future basis technology for combining optoelectronics technology with mainstream electronics manufacturing technology.
To take advantage of the existing silicon-based knowledge and infrastructure, there is a great interest in integrating active optical components into CMOS and SOI silicon technologies.
Silicon, however, is an indirect band gap semiconductor material which, unlike a direct band gap semiconductor material, has low photon emission efficiency. As a result, silicon is considered a poor source of electroluminescent radiation.
Although the photon-generation mechanism is not well understood, one source of visible light from silicon is a reverse biased p-n junction under avalanche breakdown conditions.
Avalanche breakdown occurs when the p-n junction is reverse biased and the electric field across the junction accelerates electrons into having ionizing collisions with the lattice. The ionizing collisions generate additional electrons which, along with the original electrons, are accelerated into having additional ionizing collisions. As this process continues, the number of electrons increases dramatically, producing a current multiplication effect. Building on this principle, Snyman et al. in “A Dependency of Quantum Efficiency of Silicon CMOS n pp LEDs on Current Density, IEEE Photonics Technology Letters, Vol. 17, No. 10, October 2005, pp 2041-2043”, have reported that the efficiency of light emission from silicon in a Silicon Light Emitting Device (Si LED) can be substantially increased by utilizing a reverse biased p-n junction with a wedge-shaped tip that confines the vertical and lateral electric field.
Sensor devices have been fabricated in discrete packages in order to measure physical parameters such as temperature, mechanical shock, motion, acceleration, rotation, light levels, fluid flow rate, counting of particles in a flow system, fluorescence and absorption of such particles. However these devices often require complex and sophisticated technology.
Although the sensor device can be formed on a hybrid module, further improvements of the sensor devices especially to integration and compactness are generally desirable in order to explore new applications of these devices.
What is therefore required is a sensor device which not only offers an easier integration into an existing commercially available manufacturing technology of CMOS, but also one which provides improved performance characteristics.